JERUSALEM -- A series of deadly weekend attacks has pushed Israeli Prime Minister Ariel Sharon into uncharted waters. More than ever, his political future may hinge on his ability to fend off rising criticism that he has failed to deliver on the most visible promise he made when Israelis elected him just over a year ago: enhanced security.

Palestinian militants killed at least 21 Israelis and injured more than 30 in a series of devastating weekend attacks. In Jerusalem, nine people died, including five children, when a teenage...